Method for improving oil wells



April 4, 1944.

T. Av. MOORE fn-ALV METHOD FOR IMPROVING OIL WELLS Filed Aug. 28, 1957 llll | e n a 4 Sheets-Sheet 1 April 4, 1944. T. V. MQRE TAL 2,345,713 l METHOD FOR IMPROVING OIL WELLS Filed Aug. 28, 19:57 4 sheets-sheet 2 REAGENT INLET T. v. MOORE ET AL METHOD FOR IMPROVING OIL WELLS Filed Aug. 28, 19's? 4 sheets-sheet 3 T lLUTED WA TER REA urso N0 OIL PEAGE/V7- Du. w/ TH WA T512 4 GEN TH NP April A4, 1944. T. v. MOORE l-:rAL

METHOD FOR IMPROVING OIL WELLS Filed Aug. 28, 1957` 4 Sheets-Sheet 4 OIL AND WA TER EA GEN 7- neAGEN-r w/r/v on. .AND WATER .y m w w A a o l Patented Apr. 4, .1944

, 2,345,713 METHOD FOR IMIROVING OIL WELLS Thomas V.

Moore and George E. Cannon,

Houston, Tex., assignors to Standard Oil Development Company, a corporation of Delaware y Application August 28, R1937, Serial No. 161,428

7 Claims.

This invention relates to a method of improving the productiveness of oil-producing sand by removing the water therefrom. More particularly it 'relatesto a method of increasing the flow of oil from a sand and of decreasing the flow of water from the sand.

Examination of cores of oil-producing sand has shown that from 10 to 50%, approximately, of the pore space in the sand is filled with salt water held in the interstices of the sand by interfacial forces. This Water does not move to the well with the oil as the oil is produced. We have made analyses on cores from wells in a great many producing areas and in no case has the core sample of producing sand been found to be entirely free from water. The amount of water in the sand has been determined by analyzing the core for chloride and estimating the connate water from the known ratio of chloride content of the water found below the oil bearing sand. In other cases, We have made analyses'by cutting the core while using an oil base drilling iluidin order to avoid the introduction of any extraneous water into the sand, sealing the core to prevent evaporation of 'the water, and distllling of! Athe water. 'I'he amount of water in a core taken from a given well by the last mentioned procedure is shown in the following table.

In addition to the amount of water naturally contained in these sands, the universal practice of using aqueous drilling fluids in the completion of oil wells results in the filtration of water from the drilling' into the sand withv a result that the sand. .immediately adjoining the well bore becomes Aalmost completely saturated with water. Only a portion of this water is later removed when the well produces.

We have determined that the presence of water in oil producing sand seriously reduces the permeabilityof the sand to oil. As an example, the

following results obtained by us may be cited. Kerosene was passed through sand, to 150- mesh per linear inch, packed in such a manner as to give permeability ranging from 7.8 to 8.4 darcys. 'I'he reason for using kerosene in this test instead of crude oil was that the physical properties of kerosene approximate the physical properties of crude oil under the conditions existing in typical oil reservoirs. Different samples of the sandcontained different amounts of water. The permeability of the samples to oil was determined.

In the following table, the permeability of the water-wet sand is shown as a function of the percent of pore space lled with water. The permeability of the water-wet sand to oil is expressed as percent of the permeability of the sand to oil when the sand is free from water.

Table No. 2

Percent by Relative vol. of pore permeabilspace filled ity of sand with water to oil Percent Percent It will be seen from the above table that the permeability of the sand to oil is greatly reduced if the water content of the sand exceeds 10%, by

y volume, of the pore space.

Table No. 3

Pore space Kerosene remaining velocity saturated with water Percent b1; CmJseca'nd volume The velocities ordinaruy attained in flowing oil wells are not sufllcient to reduce appreciably water saturation in the sand. For example, if

This would not be sufficient to reduce the water content of the sand to a..va1ue lower than approizimatelyI 37% by volume, as can be seen from Table No. 3. Because of this amount of water in the sand, the permeability'of the sand to oil would only be about 10% of the permeability of f the dry sand, as shown by Table No. 2.

In order to' procure the beneilts ofA increasing the permeability of the sand by removing Water therefrom, the water can be removed from the sand immediately surrounding the well, for example, to a Vdistance of one or two feet or more. When crude oil ismoving toward a well, the velocity of the oil varies inversely as the distance from the well. Consequently, the pressure drop is greater in the sand adjoining the well than it is at a greater distance, so that as much pressure is required to drive the oil through one foot of sand adjoining the well as is required to drive the oil through the next 10 feet of sandaway from the well under flowing conditions ofthe oil. increasing the permeability of the sand adjoining the well, the eie'ct on resistance to ow of the oil would be substantially the same as if the permeability of the sand were increased throughout the reservoir.

It is an object of this invention to increase the permeability of oil-bearing sand to oil and simultaneously to decrease the permeability of the sand to water. It is a further object to render the oil-bearing sand specifically wet to oil.

Other objects will be apparent from `the specification and the accompanying drawings, in which latter,

Figure 1 is a vertical sectional view through the earth showing a bore hole penetrating an oil-bearing sand and showing apparatus for ap.. plying reagent to the oil-bearing sand to remove the water.

Fig. 2 is a vertical sectional view of the well showingthe relative positions of the reagent and the oil in the'well immediately before pressure is built up to force the reagent into the .oil bearing sand.

Fig. 3 is a vertical sectional view of the oilbearing sand pierced by a bore hole showing the A disposition of the water, oil. and reagent after treatment according to this invention.V

Fig. 4 is a vertical sectional view corresponding to Fig. 3, showing diagrammatically the positions which the water and oil assume after removallof the treatment agent.

Fig. 5 is a transverse sectional view taken along the line lI-II of Fig. 3. l

Fig. 6 is a transverse sectional view taken along the line III-III of Fig. 4. A

Referring to the drawings, reference numeral I designates the ground, pierced by a bore hole 2, lined with a casing 3, supported by al casing seat 4. The bore hole 2 penetrates an oil and water bearing sand 1, and tubing 9- is disposed in the casing and terminates near Athe bottom of the bore hole. The oil bearing sand is protected by a screen I0 made an integral part of the casing by a liner 6. The tubing 9 is provided with a valve I2, and the casing 3 op'ens into a line having a valve I3. j

In preparing the well for treatment, it is desirable to circulate crude oil or distillate down through the casing 3 and up through the tubing 9 whereby any water in the bore hole is removed. While the casing is full of oil, a predetermined quantity of reagent is pumped into the casing through the valve I3. Enough reagent is pumped into the bore hole to nll considerably more than the portion of the bore hole which penetrates the oil bearing sand. 'I'he reagent. soluble in water and oil, is introduced through the valve I3 into the casing 3 until it `reaches a position opposite the oil bearing sand 1. The position of the reagent can be determined by careful volumetric measurements of the contents of the bore hole or by suitable plugs and measuring devices, not shown.

When the reagent reaches a position opposite the oil bearing sand 1, the valve I2 in the tubing 9 is closed to prevent discharge of the crude oil through the tubing 9. 'Ifhe desired quantity of reagent is followed by additional crude oil introduced through the valve I3 by suitable means such as a pump, not shown, and as a result the pressure upon vthe crude oil and upon the reagent is increased and the reagent being disposed in thebore hole adjoining the oilbearing sand is forced outwardly from the bore hole into the sand 1. Suilicient crude oil is pumped vthrough the valve I3 following the reagent so Y reagent has been effected. Zone D, most remote from the well, comprises that portion of the sand which has not been appreciably affected by the fluid pumped into the well and which containsoil and water under. the original conditions. Zone C is a portion. of the sand containing reagent that has been diluted with the water in the sand commingled with large quantities of oil. Zone B is a zone substantially lacking in free water. 'Zone A. immediately adjacent the well, comprises the portion of the sand which is fllled with the oil that was used to follow up the reagent. A

After the reagent and crude oil have been pumped into the .well to the position illustrated in Figure 3, the well is allowed to produce, establishing normal ilow of crude oil from the well under the pressures existing in the oil bearing sand. A fter the well has begun to produce, the condition?) illustrated in Fig. 4 prevail.

Zone Dvis as in Fig. 3; that is,'the portion of the sand unaiected by the treatment. Zone E comprises that portion of the sand illustrated in zones A, B and C in Fig. 3, Awhich now contain oil, since, when oil production is resumed, the oil moving through this'zone washes out the mixed reagent and water remaining, and leaves the sand free from water, or at least in such a ter than it did prior to treatment.

In order to'ftest the applicationof this'methodA loi.' increasing the permeability of theA sand to oil. we haverun experiments to determine the ilow of oil through sand bodies before and after treatment with alcohol, which was used as the reagent. lTypical experiments are described be-V low. y y

' Eject of alcohol on sand permeabilityV cess of water. 'I'he thus treated sand retained 7.1 grams of Water.

Water rate Kerosene rate 10 oc./8 seo. 10 00.120 seo.

Wata rate Kcene rate 10 00./10 secs l0 ola/13 seo.

"(b) Iso-propyl alcohol, 60- to 80-mesh sand, water wet. f

Water rate Kerosene ram 10 cc./6 sec. 10 cca/22 seo.

Water rate Kerosene rate 10 08./11 Bw. 10 00./9 sec.

'I'he reagent is a material which functions to remove water from the oil-bearingl sand. The reagent is a material which is soluble in water and oil. The properties desired in the reagent that we use are- 1. High oil solubility.ve. g., at ast or 10%, and preferably complete miscib ty with water, or at least about to 20% solubility in water.

2. It is desirable that the reagent be capable of forming a single-phase three-component system Awith the water and oil that will contain appreciable quantities of oil.

Examples of such reagents arel. Compounds containing one or more alcoholic hydroxyl groups, such as, methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, tertiary butyl alcohol, and the like.

2. Compounds containing one or more aldehyde carbonyl groups which may be immediately derived from any of the above alcoholic compounds, such as propionaldehyde and the like.

3. Compounds containing one or more ketocarbonyl groups, .such as, acetone, methyl ethyl ketone, etc.

4. Aliphatic and alicyclic acids, such as, acetic acid, propionic acid, the butyric acids, etc.

5. Compounds containing a phenolic hydroxyl group, such as phenol, resorcinol, pyrogallol, the cresols, the xylenols, etc.

6. Aliphatic, alicyclic, and aromatic compounds containing one or more amino-nitrogen atoms per molecule, such as iso-propyl amine, aniline hydrochloride, naphthylamine, and the like.

7. Esters obtained by esteriflcation of acids (4) with alcoholic compounds (l), such as ethyl acetate and the like.

8. Compounds containing two or more dissimilar groups, each of which characterizes the above mentioned compounds; such as mono, di, and triethanolamine hydroxy butyric acid, etc.

9. Compounds which may be derived from any compound of the above mentioned classes by substitution of a halogen atom, a group' containing sulfur or nitrogen, etc., for a hydrogen atom, such as chloro n-butyl alcohol, etc.

10. Aliphatic amides, such as acetamide, bu-

L tyramide and the like.

11. Mixtures ofvtwo or more of the above mentloned types of compounds.

The present invention also contemplates the use, for the aforementioned purpose, of compounds which are capable of removing the water from the sand particles by emulsification. Substances of lthis type which are preferably employed are those which are capable of forming water-in-oil emulsions. Such an agent may be supplied to the oil sand undergoing treatment in a .fr-60% solution in oil, Among the substances of this type which are useful are sulphuric acid derivatives of mineral oil, notably mineral oil sulfonates, phenol sulfnates or sulphates, oil soluble soaps, alkylolamine derivatives of high molecular weight, fatty acids and the like.

An additional feature of the present invention is the treatment of the oil sand with an agent capable of rendering the sand wettable by oil after the removal of the connate water from the sand.` It has already been proposed to treat oil sand with an agent capable of rendering it specically wettable by oil. The value of this treatment is enhanced when the connate water ls first removed from the sand according to the present invention.

Among the agents preferred for this treatment are the heavy metal soaps, particularly those of barium, zinc, tin and lead, and more specifically lead oleate. Preferably these soaps are iinely dispersed in the oil charge which is used to force the water-removing agent through the oil sand. For the purpose of the present invention this procedure is preferred over the previously proposed procedure of precipitating these agents in situ in the sand, since for the latter method the use of aqueous solutions of heavy metal salts must be resorted to.- In the method of the present invention the water inthe sand is rst removed so it is not desirable to follow'this water-removal step with a treatment of the sand with an aqueous solution. The increased eiectiveness of the agent for rendering the sand specifically wettable by oil can be obtained in part, however, byi precipitating this agent in situ from the sand from aqueous solutions of compounds capable of reacting with each other to form the agent. When this procedure is followed the aqueous solutions are forced into the oil sand after the-charge of oll used to force the water-removing agent through the sand. Alternatively, this oil charge and the water-removing agent may be removed from the sand and the aqueous solutions required to precipitate .the agent capable of rendering the bearing sand penetrated by a bore hole which comprises injecting into the sand a non-corrosive fluid soluble in water and oil whereby the water is dissolved and removing the thus formed solution from the sand. whereby the permeability of the sand to oil is increased, and subsequently treating the sand with a material capable of rendering the sand selectively wettable by oil.

2. A method for removing water from an oil rounding the bore hole of the well, and then coating thel sand grains withal nlm coating which is preferentially wettable by oil without blocking the said sand, to thereby increase the proportion of oil relative to water produced from the said sand.

5. In the method of treating an oil well to convertl a water-wet producing sand to one which is preferentially wettable by oil, the steps bearing sand penetrated by a bore hole which l of dehydrating the sand, and then ilushing the comprises two steps, one step including injecting into the sand a non-corrosive fluid soluble in water and oil whereby the water is dissolved and removing the thus formed solution from the sand, whereby the permeability of the sand to oil is increased, and the vother step including treating the sand with a material capable of rendering'the sand selectively wettable by oil.

3. A method for increasing the productivity of an oil well penetrating an oil bearing. sand which comprises forcing into the sand adjacent the well a substantially non-aqueous uid containing an agent soluble in water and in oil, and then forcing into the formation adjacent the well an oil carrying anl agent capable of rendering the sand preferentially wettable by oil. maintaining said fluids in the formation for a predetermined period of time, and then allowing the well to produce.

dehydrated sand with oil carrying a hydrophobic material to deposit 'the said material upon the sand grains and render them preferentially wettable by oil. A y

6. 'I'he method of treating an oil well to convert ay water-wet producing sand to one whichis preferentially wettable by oil, which comprises coating the sand grains throughout a substantial volume of the said producing sand surrounding the bore hole of the well witha water and crude oil-insoluble 131m coatingwhich has preferential oil wettability, in combination with the step of chemically dehydrating the said producing` tial solubility for water in the presence of the' latter. t

7. The method as defined in claim 6, in

4. The method of treating an oil well to conwhich the said producing sand is chemically devert a water wet producing sand to one which is preferentially wettable by oil, which comprises first dehydrating the sand to remove water from the pore space thereof throughout a substantial volume of the producing sand surhydrated by passing therethrough a solution of acetone.

THOMAS V. MOORE. GEORGE E. CANNON.

mineral oil 

